Amplifiers in multicarrier systems must have good large signal performance to avoid generating intermodulation distortion products at their outputs. This is particularly true in wireless receivers, which must often resolve a weaker signal among stronger signals. In dual down conversion receivers, a narrowband filter may be located after the second mixer to attenuate the strong but undesired signals and to pass the desired weak signal. By reducing the magnitude of the undesired signals, a greater fraction of the dynamic range of the amplifier circuitry in such a receiver can be used to amplify the desired signal. However, such a receiver arrangement imposes stringent requirements on the narrowband filter and other components used in the receiver.
Receivers that digitally sample the entire band of channels do not have such stringent filter requirements. However, the analog-to-digital converter and associated amplifier circuitry used in such digital sampling receivers must be able to handle large signals. When strong signals dominate, the signal-to-noise ratio of the weak signal is reduced considerably.
It is therefore an object of the present invention to provide improved circuitry for resolving weak signals from adjacent stronger signals.